WASHINGTON—A longtime State Department employee was accused of lying about her 10-year relationship with two Chinese spies who allegedly gave her and her family tens of thousands of dollars in gifts in exchange for information, according to a criminal complaint unsealed Wednesday.

The employee, Candace Claiborne, was arrested Tuesday after acknowledging in an interview with the Federal Bureau of Investigation earlier that day that she had provided the Chinese agents with information about a dissident who was being secretly housed at an embassy in an unidentified location, and with internal U.S. government perspectives on U.S.-China relations, according to court documents.

Ms. Claiborne, 60 years old, told the FBI she knew her associates were seeking the information on behalf of the Chinese government, but that she had only provided unclassified information to them, the documents say. She pleaded not guilty to charges of lying to the FBI and obstructing an official proceeding at a hearing Wednesday.

According to prosecutors, Ms. Claiborne has held a top secret security clearance since joining the State Department in 1999 and has held posts in a variety of countries, including China, Iraq and Sudan.